$ scl enable rh-python36 bash
$ python3 -V
Python 3.6.3

$ python -V  # python now also points to Python3 
Python 3.6.3

$ mkdir ~/pydev
$ cd ~/pydev

$ python3 -m venv py36-venv
$ source py36-venv/bin/activate

(py36-venv) $ python3 -m pip install ...some modules...